A continuing problem in the papermaking arts is the tendency of papers to expand or contract in size based on ambient moisture conditions. In a high moisture environment, paper fibers will generally absorb moisture and expand. As the fibers expand, the dimensions of the overall paper also expand, a phenomena referred to as hygroexpansion. On the other hand, when papers are exposed to particularly dry ambient conditions, the paper fibers may give off previously retained moisture leading to fiber and paper shrinkage. Additionally, variations in humidity conditions may lead to other variations and instabilities in the dimensions of the paper including curling and cockling.
Moreover, exposure to high humidity levels may lead to reductions in the strength and stiffiness properties of papers. This is particularly problematic in heavier paperboards that are used for packaging wherein maintenance of high strength and stiffiness is essential.
Accordingly, there is a need for papers which are less sensitive to ambient conditions and which do not tend to expand or shrink due to local moisture conditions.